The present invention relates generally to a suspension control system for an automotive vehicle for controlling damping characteristics or stiffness of a vehicular suspension system depending upon vehicle driving condition. In particular, the invention relates to an automotive suspension control system which performs anti-dive control for suppressiving nose-dive and rebounding after nose-dive, during decelation of the vehicle to a stop.
Published Japanese Utility Model Application No. (Jikkai) Sho. 56-111009, discloses a suspension system having a variable shock absorber with adjustable shock-absorbing characteristics. The shock absorber is associated with a controller for controlling the damping foce thereof. The controller operates the shock absorber to produce a higher damping force when it detects deceleration of the vehicle. The higher damping force is maintained as long as the vehicle brakes are applied to decelerate the vehicle. In other words, as soon as the brakes are released, the damping force to be produced by the shock absorber is reduced.
When applying brakes in order to stop the vehicle, the center of gravity shifts forward due to the inertia of the vehicle, which causes the vehicle "to nose dive". By adjusting the damping force to be produced by the shock absorber to HIGH, the magnitude of the nose dive can be limitted. On the other hand, at the end of vehicle deceleration, the center of gravity moves rearward, causing the front end of the vehicle to rebound. In particular, when the brake is released immediately after stopping of the vehicle, the controller operates the shock absorber to lower the damping force. This may enhance the rebounding behavior of the vehicle and degrade riding comfort.
Another approach has been discussed in the Published Japanese Patent Application (Tokkai) Showa 58-30816, in which abrupt deceleration of the vehicle is detected by means of a pressure sensor disposed within a hydraulic brake circuit. When abrupt deceleration of the vehicle is detected from the pressure sensor signal value, suspension system is hardened in order to suppress nose-dive. Such the suspension control may be successful in preventing nose-dive of the vehicle. However, since the magnitude of nose-dive is variable depending upon the deceleration of the vehicle, and rebounding magnitude after nose-dive is variable depending upon the magnitude of the nose-dive, the aforementioned suspension control system is not yet satisfactory in a sense of precise control for the suspension for precisely adopting stiffness or damping characteristics to the vehicle driving condition.